The long-range scientific goals of the proposed project are to develop flexible conducting polymers for biomedical-related applications such as artificial muscles and controlled drug delivery. Our strategy is to develop new polymeric materials, which can exhibit large conformational change with fast response time under external stimuli. One of the objectives is to introduce a polar (cyano) or hydrophilic (carboxylic acid) functional groups as the side chains of the pi-conjugated poly(1,3-phenyleneethynylene) backbone. Recent studies from our laboratories indicate that such methodology could lead to flexible conducting polymers with improved dimensional response to external stimuli, thus opening the possibility for new applications. Another main objective of the proposed research will focus on investigating molecular folding-unfolding behavior of the developed polymers via spectroscopic methods such as UV-vis and fluorescence at variable temperature. Polymer conformation in good and poor solvents will be characterized by studying the polymer solution properties such as Mark-Houwink exponent and radius of gyration. This will be coupled with study of molecular aggregation, which can be induced by changing solvent/non-solvent ratio. Combination of spectroscopic data and molecular size information will allow us to establishing a broad scientific database to understand the folding-unfolding behavior of conducting polymers. The polymers developed in this proposal may exhibit excellent dimensional responses toward external chemical and electrical stimulus. Simple devices, therefore, will be built to test the dimensional response. The goal is to develop new polymeric materials, which can exhibit a wide range of conformational change and large macroscopic deformation under the external stimulus for biomedical applications.